<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>index</title>
    <style>
      html,
      body {
        width: 100%;
        height: 100%;
        margin: 0;
        padding: 0;
      }

      body {
        display: flex;
        /* 定义body的元素垂直居中 */
        align-items: center;
        /*定义body的里的元素水平居中*/
        justify-content: center;
      }
      .content {
        width: 300px;
        height: 300px;
        background: orange;
      }
    </style>
  </head>
  <body>
    <div class="content">烦烦烦</div>
  </body>
</html>
